The long-term objective of this project is to identify the transporting mechanisms present in the ciliary body epithelial cells, and to elucidate their role, mode of action and possible interactions as relates to the secretion of aqueous humor, and regulation of cellular volume and pH. Quantitative light microscopy, fluorescence spectrophotometry, and intracellular recording will be combined to explore these mechanisms. Quantitative light microscopy will be used to measure the changes in the volume of the ciliary body epithelial cells when the tissue is exposed to changes in composition or osmolality of the surrounding medium. Fluorescence ratio microscopy will be utilized to measure changes in the intracellular activities of ions, including H+, that may underlie the volume changes, in order to identify respective ion transporters. Intracellular recordings, and the use of membrane ionophores and specific transport inhibitors will complement these studies by allowing us to decide between alternative candidates.